Multiple pole electrical switch with improved snap-action actuator structure

ABSTRACT

A multiple pole electrical switch comprising plural male and female contacts mounted on a pair of spaced contact-carrying members. The male contacts are jointly removable axially into and out of engagement with the female contacts. Movement of the male contacts is provided by a toggle mechanism which affords a rapid snap-action. Additional contact-carrying members can be stacked one above the other to increase the number of poles of the switch.

United States Patent Inventors Joseph A. Nave Villa Park; John M. Tums,Oak Park, both 01,111. Appl. No. 846,431 Filed July 31, 1969 PatentedAug. 10, I971 Assignee The Pyle-National Company Chicago, Ill.

MULTIPLE POLE ELECTRICAL SWITCH WITH IMPROVED SNAP-ACTION ACTUATORSTRUCTURE 10 Claims, 9 Drawing Figs.

U.S. Cl 200/17. 200/50 AA, ZOO/51.02, 200/78, 200/161 Int. Cl 1101b3/00, HOIh 15/18, H01h 33/46 Field of Search 200/ I 6, 51-5117,50.l5,76, 77, 78, 161, 162, 163.17, 18

Primary Examiner-.1. R. Scott Attorney-Hill, Sherman, Meroni, Gross &Simpson ABSTRACT: A multiple pole electrical switch comprising pluralmaleand female contacts mounted on a pair of spaced contact-carryingmembers. The male contacts are jointly removable axially into and out ofengagement with the female contacts. Movement of the male contacts isprovided by a toggle mechanism which affords a rapid snap-action.Additional contact-carrying members can be stacked one above the otherto increase the number of poles of the switch.

ill" 11' lll MULTIPLE POLE ELECTRICAL SWITCH WITII IMPROVED SNAP-ACTIONACTUATOR STRUCTURE BACKGROUND OF THE INVENTION This invention relatesgenerally to the field of electrical switches and more particularly todisconnect switches as utilized primarily in power supply circuits andin low-capacity control circuits.

Most main disconnect and branch circuit disconnect switches which havebeen known heretofore comprise a series of contact members generallyreferred to as knife-blades mounted in axially spaced relation on andprojecting radially from a rotating shaft. The knife-blade members aremoved into and out of engagement with a corresponding number ofspring-clip contact members mounted stationarily on the frame or cabinetenclosure of the switch.

The number of poles, that is, the number of pairs of knifeblade andspring-clip contacts in known disconnect switches is generally limitedto no more than four and all the poles of any given switch are generallyconstructed to accommodate the same current and voltage.

In such known disconnect switches it is generally impossible orinfeasible to increase the number of poles. First of all, an increase inthe number of poles normally requires an increase in the length of theshaft on which the knife-blade contacts are mounted and this oftenrequires an increase in the width of the cabinet which encloses theswitch. Secondly, additional knifeblade contacts and clip contactscannot easily be added in the field due to the type of constructionnormally employed in the manufacture of disconnect switches.

Another deficiency in known disconnect switches involves the inabilityto simultaneously connect and disconnect main power circuits along withlow voltage control circuits. Since all of the contacts in any givenprior art disconnect switch are sized to accommodate a given powerlevel, it is impractical to utilize a single disconnect switch of theprior art for both main power and low voltage control circuitapplications.

Other deficiencies of prior disconnect switches involve problems ofservice and maintenance of the switches. For example, to replace asingle knife-blade contact it is generally necessary to completelyremove the shaft upon which the knifeblade contacts are mounted, and, inmany cases, many of the blade contacts mounted on the shaft, thus notonly increasing maintenance costs but also precluding operation of theremaining operable contacts during service operations.

To. generally improve the art of disconnect switches, to enable mainpower supply and low voltage control circuits to be actuated by a singledevice, to enable additional poles to be easily added to existingswitches and to reduce service and maintenance costs are among importantobjects of the present invention.

SUMMARY OF THE INVENTION The present invention may be summarized ascomprising a multiple pole electrical switch in which a pair ofcontact-carrying members are employed to mount a plurality of male andfemale contact members which are rectilinearly relatively axiallyshiftable in unison into and out of engagement with one another.Additional pairs of contact-carrying members may be stacked one abovethe other in modular arrangement to increase the number of poles of theswitch and to provide contacts of various capacities in order toaccommodate both main power supply current and low control circuitcurrent in a single switch.

The invention features a toggle mechanism for increasing the engagingand disengaging speeds of the contacts. The flat" or rectilinearswitching motion of the contacts reduces the silhouette of the switchenclosure and enables the enclosure to more readily accommodate a flatenclosure door on which may be mounted auxiliary devices such as pilotlights, pushbutton stations and selector switches. The enclosure doormay be made of transparent material such as clear plastic to afford easyinternal inspection and testing of the switch.

The flat or rectilinear movement of the contacts also reduces thepossibility of interference with the operation thereof. The modularconstruction facilitates repair or maintenance since individual modulescan be replaced independently of one another and operation of thecontacts of one pair of modules can continue while other modules areremoved for repair or replacement.

Many other features, advantages and additional objects of the presentinvention will become manifest to those versed in the art upon makingreference to the detailed description which follows and the accompanyingsheets of drawings in which a preferred structural embodimentincorporating the principles of the present invention are shown by wayof illustrative example only.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a top plan view of a multiplepole electrical switch constructed in accordance with the principles ofthe present invention.

FIG. 2 is a vertical cross-sectional view taken II-II of FIG. 1position.

FIG. 3 is similar to FIG. 2 but illustrates the switch in a closed orengaged position.

FIG. 4 is an enlarged top plan view of the operating handle assembly ofthe switch.

FIGS. 5, 6 and 7 are respectively front, left end and right endelevational'views of one member of the handle assembly.

FIG. 8 is an enlarged sectional view taken substantially along linesIV-IV of FIG. 1, the illustration of certain parts of the switch havingbeen omitted for clarity.

' :FIG. 9 is similar to FIG. 4 but illustrates the pin contacts in theengaged positions thereof.

along lines showing the switch in an open or disengaged DESCRIPTION OFTHE PREFERRED EMBODIMENT In the drawing reference numeral 10 indicatesgenerally a multiple pole electrical switch constructed in accordancewith the principles of the present invention. The switchlt) may be moreparticularly characterized as comprising a frame 11 having asubstantially planar top surface 12. Projecting upwardly from thesurface 12 at one side 13 of frame 11 are a pair of pedestals l4 and 16and. along an opposite side 17 a pair of pedestals I8 and'l9.

'Fastenedsecurely to the planar surface 12 are a pair ofcontact-carrying members indicated respectively at reference charactersM and F. The members M and F are disposed in mutually aligned relationwith one another along the longitudinal axis of the frame 11 andcomprise vertical end walls 20 and 21 which are disposed inlongitudinally spaced relation with one another.

Formed in the member F are a plurality of longitudinally extendingcylindrical bores, one of which is indicated at reference numeral 22,disposed in spaced relation in a direction transversetothe axis of theframe 11 and arranged in mutually parallel relation. In the illustratedembodiment of the invention the female contact-carrying member F hasfour bores 22'formed therein but it should be understood that thisnumber is not inflexible and can be easily increased or reduced asspecific requirements may dictate.

Each of the bores 22 extends through an aperture 23 formed in thevertical'end'wall 21 of the member F, the apertures 23 eachbeing flaredto provide a tapered mouth to the entrance of its respective bore 22.

Fixedly secured withineach of the bores 22 is a female contact member 24having formed therein a cylindrical bore 26 axially aligned with itscorresponding aperture 23. The contacts 26, unlike the contact-carryingmember F, are made of electrically conductive material such as metal.

Formed in the male contact-carrying member M are a corresponding numberof bores 27 each of which is axially aligned with a counterpart bore 22.Disposed stationarily within each of the bores 27 is a member 28 similarto the female contacts 24 and cylindrically bored as at 29 to receivetherein a male pin contact indicated at reference numeral 30. The malecontact 30 is not secured to the member 28 but instead is slidableaxially within the bore 29. Also carried on the contact-carrying membersM and F are terminals for receiving the ends of electrical conductorssuch as wires. One terminal is provided for each of the female contacts24 and the members 28. It will be appreciated that the members 28 aswell as the male contacts 30 are also made of electrical conductivematerial whereas the contact-carrying member M, like member F, is madeof suitable insulation material such as rigid plastic.

The male contacts 30 are interconnected by a transversely extendingcontact-connecting block 31. The block 31 may be fabricated in two parts310 and 31b to accommodate a raised rib 32 formed on each of the malecontacts 30 and the two parts 310 and 31b may be suitably bondedtogether to provide a single block member 31.

FIGS. 4 and 5 illustrate that the block 31 is shiftable back and forthbetween the end walls 20 and 21 of the contact-carrying members M and Fand as it shifts back and forth it alternately engages and disengages atapered nose end 33 of each of the male contacts 30 with a correspondingfemale contact 24. The male contacts 30 are of sufficient length so thatin the closed or engaged position of the switch a substantial portion ofeach of the male contacts still resides in its respective bore 29 sothat a sufficient and suitable journal is provided and any substantialtransverse movement or flexing of the male contacts 30 is prevented.

Thus, to engage and disengage the male contacts 30 from the femalecontacts 24 the male contacts 30 are shifted axially and rectilinearlywithin their corresponding contact-carrying member M for telescopicengagement and disengagement of the nose ends thereof with the femalecontacts. It will be appreciated that this straight line movement of themale contacts 30 is altogether different from the swinging or pivotingmovement of the knife-blade contacts of prior art disconnect switches.

The present invention contemplates the provision of means forfacilitating an addition or reduction in the number of poles or pairs ofmale and female contacts. As illustrated in the drawing another malecontact-carrying member M is stacked directly on top of member M andanother female contact-carrying member F is stacked on top of member F.Corresponding female and male contacts 24' and 30' are carried bymembers F and M and are arranged in axially aligned relation similar tothe axially aligned arrangement of contacts 24 and 30.

The number of contacts 24 and 30' may be equal to or different from thenumber of contacts 24 and 30 and as illustrated may be of differentphysical sizes to accommodate different electrical loads. It will alsobe apparent that the physical sizes including the diameters of therespective contacts 24 and 30 may differ from one another and a similarobservation is made with respect to the female or male contacts 24 and30.

Thus each of the pairs of contacts may be sized to accommodate apredetermined load. Some pairs of contacts in a single switch 10 may beutilized in main power supply circuits whereas others may be utilized inlow voltage control circuits or the like. The present inventiontherefore affords maximum flexibility not only in terms of the number ofpoles which the switch 10 may accommodate (additional contact-carryingmembers may be stacked one above the other) but also in terms ofvariations in the loads of the various circuits in which the poles areconnected.

The current carrying members M and F are also provided with a malecontact-connecting block 31 for joint shifting of the male contacts 30.In the illustrated embodiment the block members 31 and 31' are bonded orotherwise suitably interconnected forjoint movement whereby both sets ofmale contacts 30 and 30 are shifted back and forth simultaneously.

In order to shift the blocks 31 and 31' and thus to engage and disengagethe male and female contacts the invention includes switch operatingmeans which is indicated generally in the drawing at reference numeral34. Switch-operating means 34 comprises a carrier member 36 engagedlyconnected to one end 37 of the block member 31 and having projectingtherefrom a pin 38. The carrier member 36 is slidably carried on thesurface 12 of the frame 11 and is guided back and forth between endwalls 39 and 40 of the pedestals 14 and 16 by a cylindrical guide way36a extending between the pedestals 14 and 16 and received in a bore 36bformed in the carrier 36.

The carrier 36 (and thus the block members 31 and 31) are shifted backand forth by means of a bracket 41 mounted on a shaft 42 which isjournaled for rotation on the frame 11. The bracket 41 is yoke-shapedand comprises a pair of radially extending legs 43 and 44 which arespaced angularly from one another and between which is confined the pin38.

Also mounted on shaft 42 is one arm 46 of an overcenter spring-biasedtoggle mechanism 47, the other arm of which is indicated at referencenumeral 48. The two arms 46 and 48 are pivotally interconnected at 49and an upper end 50 of the arm 48 is mounted on a bracket 50a pivotallysecured to a protruding portion 51 of the pedestal 16. A helical spring52 is wound about the arm 48 and is placed in a state of furthercompression as the arms 46 and 48 are brought into alignment with oneanother as will be understood by those skilled in the art.

As shown in FIGS. 47, the shaft 42 is journaled in a bearing 53 formedon the frame 11. The bracket 41 is locked for joint rotation with theshaft 42 by means of a pin 41a which is press fit into aligned boresformed in the bracket 41 and the shaft 42. The arm 46 is also locked toshaft 42 for joint rotation, and for that purpose a pin 46a is press fitinto aligned bores in the shaft 42 and the arm 46.

Pin 46a, however, extends at both its ends radially outwardly beyond theouter surface of the arm 46. The ends of pin 46a are disposed in aradial slot 54a formed in an end wall 54b of a handle shaft indicated atreference numeral 54. A bore 540 is also formed in the end wall 54b toreceive the end of the shaft 42. i Y

The shaft 54 is journaled for rotation in a bearing member 55 threadedinto an embossment 56a formed on a sidewall 56b ofa cabinet 56 in whichthe assembly 10 is housed. A reduced diameter portion 54d of shaft 54and a rectangularly shaped stub end 54c extending axially therefrom arereceived in a complimentarily shaped bore formed in a handle 57, and thehandle 57 is connected fast to the shaft 54 by means of a pin 57a pressfit into aligned bores 57b and 54f formed respectively in the handle 57and the shaft 54.

In operation the handle 57 is selectively pivoted back and forth to movethe male contacts such as contacts 30 into and out of electricalengagement with their corresponding female contacts 24. For example, inthe disposition of the parts shown in FIGS. 1 and 2 the male contacts 30are spaced from and are out of engagement with their correspondingfemale contacts 34. To engage the contacts the handle 57 is pivoted torotate the shaft 54 so that a sidewall 54g of the slot 54a engages thepin 46a to rotate the shaft 42 in a clockwise direction to the positionthereof shown in FIG. 2.

As the shaft 42 begins to rotate clockwise the yoke-shaped bracket 41member immediately begins to rotate in a clockwise direction, but thecarrier 36 does not move immediately due to the lost-motion drivingconnection between the legs 43 and 44 of the bracket 41 and the pin 38.

After the handle 47 has been rotated substantially through its fulloperating arc of movement in a clockwise direction the arm 46 of thetoggle mechanism 47 is brought into longitudinal alignment with the arm48. The spring 52 then biases the arm 46 (and thus the bracket 41) in aclockwise direction, thereby quickly moving the leg 43 into abutmentwith the pin 38 and shifting the carrier member 36 and the block 31 tothe engaged or closed positions thereof as illustrated in FIG. 3.

The operation of the switch 10 may be conveniently referred to ascomprising a snap-action as a result of the lostmotion connectionbetween the yoke-shaped member 41 and the pin 38 and as a result of theoperation of the overcenter spring-biased toggle mechanism 47. The malecontacts may therefore be very rapidly engaged with and withdrawn from"the female contacts, thereby reducing arcing and deterioration of thecontacts.

The width of the slot 54a is sufficient to permit free rotationalmovement of the pin 46a once the snap-action of the switch movementoccurs. This oversized width of the slot 540 prevents inadvertentrestraint or braking" of the snap-action by the operator by holding thehandle 57 after the snap-action begins.

The switch frame 11 is secured to a bottom wall 58 of the cabinet 56 bymeans of a plurality of fasteners such as the threaded nuts and boltsindicated at 59 and 60 and is spaced from the bottom wall 58 by means ofa plurality of spacer blocks 61 through which the bolts 59 extend. Thetop face of the cabinet 56 may be covered by means of a clear plasticplate or the like as indicated at reference numeral 62 to enclose thecabinet 56 while affording ready visual inspection of the operation andthe various parts of the switch 10.

The internal parts of the switch including the frame 11 may be easilyremoved from the cabinet 56 for repair or for replacement by anotherinterior with a different contact configuration. Thus it is merelynecessary to loosen the fasteners 59 and 60, thereby loosening the frame11 from cabinet 56. Then the frame in its entirety can be removed bysliding it out such that the end of shaft 42 and pin 46a disengageshandle shaft 54, more specifically bore 540 and radial slot 54a.

The invention also contemplates the provision of a safety lock forpreventing inadvertent closing or engaging of the male and femalecontacts. As illustrated, a lock arm 63 is pivotally mounted on athreaded stud 64 which is fastened to the pedestal 14. Wound about thestud 64 is a spring 66 one end ofwhich is stationarily secured at 67 andthe other end of which is inturned over the arm 63 as at referencenumeral 68. The arm 63 is therefore biased in a counterclockwisedirection.

A locking finger 69 extends from the arm 63 and comprises an embossment70 forming a shoulder 71 and a cutout 72. In the arrangement of theparts shown in FIG. 2 the shoulder 71 abuttingly engages acomplementarily arcuately shaped shoulder 73 formed on the yoke-shapedmember 71. The wall 72 is thereby disposed with respect to a sidewall 74of the yoke-shaped member 41 to prevent rotation of member 41 in aclockwise direction to cause engagement of the male and female contacts.

In order to close the switch 10 it is necessary to rotate the arm 63 ina clockwise direction to the position thereof shown in FIG. 3, therebyremoving the shoulder 72 from the path of movement of the bracket 41.After the arm has been rotated clockwise the requisite number of degreesand the handle 57 has been rotated slightly clockwise, the arm 63 may bereleased and a bottom wall 76 of the arm 69 will continue to ride on thearcuate shoulder 73 of the member 41.

When the handle 57 is turned in a counterclockwise direction to open theswitch 10, the arm 63 will automatically pivot in a counterclockwisedirection to lock the yoke-shaped member in place, thereby precludingsubsequent closing of the switch 10 until the arm 63 is rotated to thenonlocking position thereof shown in FIG. 3.

The function of the safety lock is to prevent inadvertent closing of theswitch with the cabinet cover open. The cover contains a suitablebracket such that when it is closed the bracket depresses the L-shapedupper end of the lock arm 63 rotating :63 from a position shown in FIG.2 to a position shown in FIG. 3. Thus the switch can be turned ON." Asthe yoke 41 rotates to the position in FIG. 3, it rotates lock arm63additionally to engage the L shaped end of 63 with a suitable bracket inthe cover precluding the opening of the cover with the switch in theengaged position. When the switch is turned OFF, the lock arm 63 isallowed to rotate sufficiently back to disengage 63 from the cover andallowing the cover to be opened for inspection orservicing.

Although minor modifications may be suggested by those versed in theart, it should be understood that we wish to embody within the scope ofthe patent warranted hereon all such modifications as reasonably comewithin the scope of our contribution to the art.

We claim:

1. A multiple pole electrical switch comprising an elongated switchframe,

a pair of contact-carrying members fixedly secured to said frame andhaving transverse sidewalls facing one another in longitudinally spacedrelation,

a plurality of longitudinally extending bores formed in each of saidmembers axially aligned with one another and opening to said transversesidewalls,

female contacts mounted in the bores of one of said members and malecontacts carried in the bores of the other member for slidable movementonly in an axial direction, means between said sidewalls forming a malecontact interconnecting block for providing joint movement of said malecontacts,

means including a block-shifting arm mounted on said frame for pivotalmovement about an axis transverse to the longitudinal axis of said frameand having means engageable with said block means for shifting saidblock means back and forthto move said male contacts axially into andout of engagement with said female contacts, and means for selectivelypivoting said block-shifting arm.

2. The invention as defined in claim 1 wherein said block meanscomprises an operating pin projecting transversely of said frame andsaid block-shifting arm comprises a yokeshaped member having a pair ofradial legs extending on opposite sides of said operating pin'forengaging and moving said pin back and forth longitudinally of said framein response to pivotal movement of said yoke-shaped member.

3. The invention as defined in claim 2 wherein said radial legs areangularly spacedto provide lost motion between said yoke-shaped memberand'saidoperating pin.

4. The invention as defined in claim' 3 and including a pivotal shaftmounting said yoke-shaped member and an overcenter spring-biased togglemechanism mounted on said frame and connected to said shaft to provide asnap-action pivotal movement of saidshaft.

5. The invention as defined in claim 4 and including cabinet meanshaving a bottom wall and a sidewall,

meansmounting said switch frame on said bottom wall,

means in said sidewall for receiving said rotatable shaft,

handle means outside said-sidewall and means corotatably interconnectingsaid handle means and said shaft.

6. The invention as defined in claim 5 wherein said interconnectingmeans comprises anothershaft axially alignedwith said shaft,

a handle mounted'fast' on said other shaft, and

cooperating radial pinand slot means on said shafts for interconnectingsaid.shafts for joint rotation and for limited relative rotation.

7. The invention as definedin claim 1 and includingv another pair ofcontact-carrying members stacked on top of and-fixedly securedtosaidfirst pair, and

corresponding male'and femalecontacts in said second pair ofcontact-carryingmem bers,

said block means also interconnecting themule contacts of saidsecondpair of contact-carrying members for joint movement thereof-withsaid male contacts of-said first pair.

8. A- multiple: pole-electrical switch comprising'a switch frame, apair" of contact-carrying members stationarily mounted on'saidtframein'spacedrelation to one another and having axially aligned bores formedtherein and opening toward'one'another,

female; contacts stationarily-disposed:in'said bores'of one of saidcontact-carryingmembers,

block means for shifting same back and forth between saidcontact-carrying members.

9. The invention as defined in claim 8 wherein said guide way meanscomprises a plurality of elongated guide ways extending between saidcontact-carrying members and means forming bores extending through saidblock means for receiving said guide ways.

10. The invention as defined in claim 8 wherein said snapaction meanscomprises a lost-motion spring-biased toggle mechanism.

1. A multiple pole electrical switch comprising an elongated switchframe, a pair of contact-carrying members fixedly secured to said frameand having transverse sidewalls facing one another in longitudinallyspaced relation, a plurality of longitudinally extending bores formed ineach of said members axially aligned with one another and opening tosaid transverse sidewalls, female contacts mounted in the bores of oneof said members and male contacts carried in the bores of the othermember for slidable movement only in an axial direction, means betweensaid sidewalls forming a male contact interconnecting block forproviding joint movement of said male contacts, means including ablock-shifting arm mounted on said frame for pivotal movement about anaxis transverse to the longitudinal axis of said frame and having meansengageable with said block means for shifting said block means back andforth to move said male contacts axially into and out of engagement withsaid female contacts, and means for selectively pivoting saidblockshifting arm.
 2. The invention as defined in claim 1 wherein saidblock means comprises an operating pin projecting transversely of saidframe and said block-shifting arm comprises a yoke-shaped member havinga pair of radial legs extending on opposite sides of said operating pinfor engaging and moving said pin back and forth longitudinally of saidframe in response to pivotal movement of said yoke-shaped member.
 3. Theinvention as defined in claim 2 wherein said radial legs are angularlyspaced to provide lost motion between said yoke-shaped member and saidoperating pin.
 4. The invention as defined in claim 3 and including apivotal shaft mounting said yoke-shaped member and an overcenterspring-biased toggle mechanism mounted on said fRame and connected tosaid shaft to provide a snap-action pivotal movement of said shaft. 5.The invention as defined in claim 4 and including cabinet means having abottom wall and a sidewall, means mounting said switch frame on saidbottom wall, means in said sidewall for receiving said rotatable shaft,handle means outside said sidewall and means corotatably interconnectingsaid handle means and said shaft.
 6. The invention as defined in claim 5wherein said interconnecting means comprises another shaft axiallyaligned with said shaft, a handle mounted fast on said other shaft, andcooperating radial pin and slot means on said shafts for interconnectingsaid shafts for joint rotation and for limited relative rotation.
 7. Theinvention as defined in claim 1 and including another pair ofcontact-carrying members stacked on top of and fixedly secured to saidfirst pair, and corresponding male and female contacts in said secondpair of contacts-carrying members, said block means also interconnectingthe male contacts of said second pair of contact-carrying members forjoint movement thereof with said male contacts of said first pair.
 8. Amultiple pole electrical switch comprising a switch frame, a pair ofcontact-carrying members stationarily mounted on said frame in spacedrelation to one another and having axially aligned bores formed thereinand opening toward one another, female, contacts stationarily disposedin said bores of one of said contact-carrying members, male contactsslidably carried in said bores of the other of said contact-carryingmembers and movable axially between a first position at which they arespaced from said female contacts and a second position at which they aretelescopically engaged with said female contacts, block meansinterconnecting said male contacts for joint movement and disposed forback-and-forth movement between said contact-carrying members, guide waymeans for guiding said block means in rectilinear movement only to movesaid male contacts axially between said first and second positionsthereof, and means including snap-action means engageable with saidblock means for shifting same back and forth between saidcontact-carrying members.
 9. The invention as defined in claim 8 whereinsaid guide way means comprises a plurality of elongated guide waysextending between said contact-carrying members and means forming boresextending through said block means for receiving said guide ways. 10.The invention as defined in claim 8 wherein said snap-action meanscomprises a lost-motion spring-biased toggle mechanism.